Why people vote similarly – and what that reveals about political division

Electoral research has long assumed that people make their decisions primarily on the basis of individual convictions, political programmes and personal interests. However, a new study by Prof. Dr Nils-Christian Bormann, conflict researcher at the University of Witten/Herdecke (UW/H), shows that political decisions are strongly influenced by social affiliations - most strongly by language and regional origin.

New method makes voting behaviour comparable

To prove this, Bormann has developed a new method known as "covoting regression". It fundamentally changes the way we look at voting behaviour: instead of looking at individual decisions, it examines the similarities between two people who vote the same way. "These patterns reveal how strongly political decisions are anchored in social structures," says Bormann.

The method makes it possible for the first time to compare voting behaviour across countries, time periods and different party systems.

Origin and language as the strongest influencing factor on voting behaviour

The results are clear: coethnicity - i.e. common ethnic or linguistic affiliation - is the strongest driver for people to vote in the same way. They often receive the same information, read the same media, follow similar sources or talk to people who think similarly. The resulting effect is around four times greater than that of traditional characteristics such as income, education, religion or urban-rural differences.

The analysis is based on data from countries south of the Sahara. There, this correlation remains stable over time. Voting behaviour therefore follows less short-term political debates than long-term social ties.

What the results of the study mean for Europe

The results are also relevant for Europe - because there, too, the pattern is evident wherever language and identity draw regional boundaries. In Belgium, the political dividing line runs along the border between Flemish and French, in Spain between Catalan and Castilian. People there not only vote for different parties - they make their decisions based on fundamentally different social contexts.

This is precisely one of the central mechanisms of polarisation: political differences are not only based on opinions, but also on social affiliations - making them more stable and harder to bridge.

In Germany, the effect is weaker, but recognisable. The CSU in Bavaria is the clearest example: regional identity and dialect signalise affiliation. This is reflected in voting behaviour. Studies suggest that similar patterns could also be seen in the rise of the AfD.

Bormann and his team are currently working on a Europe-wide study. It aims to measure more precisely which social affiliations are politically decisive in different countries - and how these patterns change.

Further information:

The study was published in the American Political Science Review. The most prestigious journal of political science: https://doi.org/10.1017/S0003055426101579